Norovirus (sometimes misspelled “noreau virus”) is a highly contagious virus that causes sudden vomiting and diarrhea, often called the “stomach flu” even though it has nothing to do with influenza. It is the leading cause of acute gastrointestinal illness worldwide, responsible for an estimated 685 million cases of diarrhea and over 200,000 deaths each year, with the vast majority of those deaths occurring in developing countries. The virus was first identified after an outbreak of gastroenteritis in Norwalk, Ohio, in 1968, which is why it was originally called “Norwalk virus.”
How Norovirus Makes You Sick
Norovirus is a small, sturdy RNA virus that belongs to a family called Caliciviridae. Unlike many viruses, it lacks an outer fatty envelope, which is part of what makes it so hard to kill on surfaces and so resistant to common disinfectants. Once it enters your body, it inflames the lining of your stomach and intestines, triggering the intense vomiting and diarrhea the virus is known for.
Symptoms typically hit fast. Most people start feeling sick 12 to 48 hours after exposure, and the worst of it usually lasts one to three days. Along with vomiting and diarrhea, you may experience stomach cramps, nausea, low-grade fever, and body aches. The illness is miserable but usually resolves on its own in otherwise healthy adults.
Why It Spreads So Easily
Norovirus spreads through the fecal-oral route, which sounds clinical but simply means tiny particles of stool or vomit from an infected person end up in someone else’s mouth. That can happen in several ways: touching a contaminated surface and then touching your face, eating food prepared by someone who is sick, drinking contaminated water, or even breathing in fine droplets that spray into the air when someone nearby vomits.
Certain foods carry higher risk. Raw shellfish, especially oysters, are a frequent source because these filter feeders concentrate viral particles from contaminated water in their tissue. Ready-to-eat cold foods like salads and sandwiches are also common culprits, since they aren’t cooked before serving. Contaminated ice has triggered outbreaks as well.
The virus is notoriously persistent in the environment. Norovirus particles can remain infectious on hard surfaces for up to two weeks and can survive in water for more than two months. This environmental toughness is why outbreaks recur so easily in confined settings. On cruise ships, for instance, contamination left behind after one outbreak has sickened newly boarded passengers on the very next voyage. Similar transmission has been documented on airplanes, where contaminated lavatories or a single symptomatic passenger can spread the virus to others in the cabin.
Who Is Most at Risk
Anyone can catch norovirus, but the consequences are most serious for young children, older adults, and people with weakened immune systems. The main danger is dehydration from the rapid loss of fluids through vomiting and diarrhea. Young children and elderly adults are less able to replace fluids quickly enough, which is why approximately 99% of norovirus deaths occur in developing countries where access to rehydration care is limited.
Treatment and Recovery
There is no antiviral medication for norovirus, and antibiotics are useless against it since it’s a viral infection. Treatment focuses entirely on replacing the fluids and electrolytes your body is losing. For most adults, that means drinking water, broth, sports drinks, or fruit juice in small, frequent sips, especially if vomiting makes it hard to keep anything down. Saltine crackers can also help replace electrolytes.
For children, pediatric oral rehydration solutions (like Pedialyte) are the best option because they contain the right balance of glucose and electrolytes for smaller bodies. Plain water alone isn’t ideal for kids with significant vomiting or diarrhea because it doesn’t replace the salts they’re losing.
Most people recover fully within one to three days without medical intervention. However, even after you feel better, you remain contagious. The virus continues to shed in your stool for days after symptoms resolve, which is why careful hand hygiene after recovery matters just as much as during the illness itself.
Why Hand Sanitizer Isn’t Enough
One of the most important things to know about norovirus is that alcohol-based hand sanitizers are not a reliable defense against it. Because the virus lacks a fatty outer envelope, alcohol doesn’t break it apart the way it does with many other germs. Research from long-term care facilities found that staff who relied on hand sanitizers as much as or more than soap and water were six times more likely to work in a facility that experienced a norovirus outbreak. Among facilities where hand sanitizers were the preferred method, 53% had a confirmed outbreak, compared with just 18% of facilities that used soap and water more often.
The CDC specifically recommends against using hand sanitizer as a substitute for handwashing when it comes to norovirus. Washing your hands with soap and water for at least 20 seconds is the single most effective way to remove the virus from your skin.
Cleaning Contaminated Surfaces
Standard household cleaners often aren’t strong enough to kill norovirus on countertops, bathroom fixtures, or floors. The CDC recommends using a chlorine bleach solution at a concentration of 1,000 to 5,000 parts per million, which works out to roughly 5 to 25 tablespoons of regular household bleach (5% to 8% concentration) per gallon of water. Alternatively, you can use a disinfectant that’s specifically registered with the EPA as effective against norovirus.
If someone in your household is sick, cleaning visibly soiled areas isn’t sufficient. The virus can linger on surfaces that look clean, so disinfecting bathrooms, door handles, light switches, and any surface the sick person has touched is important for preventing spread to others in the home. Given that the virus can survive on surfaces for up to two weeks, a single wipe-down right after the illness may not be enough in high-traffic areas.
How to Reduce Your Risk
- Wash hands thoroughly with soap and water for at least 20 seconds, especially before eating, after using the bathroom, and after changing diapers.
- Avoid preparing food for others while you’re sick and for at least two days after symptoms stop.
- Rinse fruits and vegetables and cook shellfish to an internal temperature of at least 145°F, though even thorough cooking doesn’t eliminate all risk with oysters.
- Disinfect surfaces with a bleach solution or an EPA-registered norovirus disinfectant, not just an all-purpose spray.
- Wash contaminated laundry promptly, using the hottest appropriate water setting and machine drying.
Norovirus is extremely common and, for most people, a short-lived but unpleasant illness. Understanding how it spreads and how to properly clean after an infection makes a real difference in protecting the people around you, particularly those who are more vulnerable to serious dehydration.